Up to now, except for isolated $states^{1,2}$, the spin-rotation interaction in $NO_{2}$ has been treated using a perturbation $method^{3}$. In the present work, an extensive analysis of $NO_{2}$ Fourier transform spectra in the 6.3 $\mu m$ region has been performed leading to a large and precise set of spin-rotation levels of the (001),(020) and (100) interacting states of this molecule. Then, using an Hamiltonian which takes explicitly into account the Coriolis-type interaction between the levels of (001) and (020) and between those of (001) and (100) as well as the spin-rotation interaction, it has been possible to reproduce very satisfactorily the observed energy levels even in the case of strong resonances. Examples of the effects of such resonances will be given showing clearly that one needs to take them explicitly into account in order to reproduce within the experimental uncertainty the observed spectra. $^{1}$A. Perrin, J-M. Flaud, C. Camy-Peyret. B. Carli and M. Carlotti, Molec. Phys. 63, 791 (1988) $^{2}$A. Perrin, C. Camy-Peyret, J-M. Flaud and J. Kauppinen, J. Mol. Spectrosc. 130, 168 (1988) $^{3}$W. T. Raynes, J. Chem. Phys. 41, 3020 (1964)